Structural Study of a [100] 45° Twist Plus 7.5° Tilt Grain Boundary in Aluminium by HREM

1999 ◽  
Vol 589 ◽  
Author(s):  
M. Shamsuzzoha ◽  
P. A. Deymier ◽  
David J. Smith
Keyword(s):  
Grain Boundary ◽  
High Resolution Electron Microscopy ◽  
Image Features ◽  
Boundary Structure ◽  
High Concentration ◽  
Atomic Column ◽  
Resolution Electron ◽  
Cold Rolling And Annealing ◽  
Tilt Grain Boundary ◽  
Local Relaxation

AbstractA [100] 45° twist plus 7.5° tilt grain boundary in aluminium prepared by cold rolling and annealing has been studied by high-resolution electron microscopy. The direct interpretability of the image features in terms of atomic column positions allows structural models of the grain boundary to be developed. The boundary exibits a high concentration of steps due to the 7.5° tilt from a perfect [100] 45° quasiperiodic misorientation. Occurrence of co-incidence and pseudo co-incidence of atomic planes across the interface appears to play an important role in the formation of steps along this boundary. Local relaxation of atoms resulting from the perturbation of the [100] 45° twist bi-crystal determines the boundary structure

Atomic Structure of 66° [110] Asymmetric Tilt Grain Boundary in Aluminum

1996 ◽  
Vol 466 ◽  
Author(s):  
M. Shamsuzzoha ◽  
P. A. Deymier ◽  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
High Resolution Electron Microscopy ◽  
Structural Features ◽  
Resolution Electron ◽  
Cold Rolling And Annealing ◽  
Line Defects ◽  
Tilt Grain Boundary ◽  
Straight Segments

ABSTRACTA 66° [110] asymmetric tilt grain boundary in Al prepared by cold rolling and annealing has been studied by high-resolution electron microscopy. Due to a 4.5° deviation from the perfect Σ3 misorientation, the boundary is heavily faceted with straight segments running parallel to (111) and (112) planes. All atomic sites across the (111) facets appear to be coincident with the (111) planes at an angle of 66°. The line defects which accommodate the deviation from the perfect twin orientation result in grain boundary stepping. The observed structural features can be described in terms of secondary grain boundary dislocations with Burgers vectors of the type ⅓<111>, and ⅙<112> as well as their interactions.

Σ =13 tilt grain boundary in silicon bicrystal

1990 ◽  
Vol 48 (4) ◽  
pp. 562-563
Author(s):  
M.J. Kim ◽  
Y.L. Chen ◽  
R.W. Carpenter ◽  
J.C. Barry ◽  
G.H. Schwuttke
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Rotation Axis ◽  
Czochralski Method ◽  
High Resolution Electron Microscopy ◽  
Image Simulation ◽  
Simulation Techniques ◽  
Resolution Electron ◽  
The Common ◽  
Tilt Grain Boundary

The structure of grain boundaries (GBs) in metals, semiconductors and ceramics is of considerable interest because of their influence on physical properties. Progress in understanding the structure of grain boundaries at the atomic level has been made by high resolution electron microscopy (HREM) . In the present study, a Σ=13, (510) <001>-tilt grain boundary in silicon was characterized by HREM in conjunction with digital image processing and computer image simulation techniques.The bicrystals were grown from the melt by the Czochralski method, using preoriented seeds. Specimens for TEM observations were cut from the bicrystals perpendicular to the common rotation axis of pure tilt grain boundary, and were mechanically dimpled and then ion-milled to electron transparency. The degree of misorientation between the common <001> axis of the bicrystal was measured by CBED in a Philips EM 400ST/FEG: it was found to be less than 1 mrad. HREM was performed at 200 kV in an ISI-002B and at 400 kv in a JEM-4000EX.

Structural Transformation of a Germanium Σ=13 (510) [001] Tilt Grain Boundary under the Electron Beam

1990 ◽  
Vol 48 (1) ◽  
pp. 52-53 ◽  
Author(s):  
Jean-Luc Rouvière ◽  
Alain Bourret
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Structural Transformation ◽  
Mirror Symmetry ◽  
High Resolution Electron Microscopy ◽  
Structural Transformations ◽  
Covalent Bonds ◽  
Resolution Electron ◽  
Tilt Grain Boundary

The possible structural transformations during the sample preparations and the sample observations are important issues in electron microscopy. Several publications of High Resolution Electron Microscopy (HREM) have reported that structural transformations and evaporation of the thin parts of a specimen could happen in the microscope. Diffusion and preferential etchings could also occur during the sample preparation.Here we report a structural transformation of a germanium Σ=13 (510) [001] tilt grain boundary that occurred in a medium-voltage electron microscopy (JEOL 400KV).Among the different (001) tilt grain boundaries whose atomic structures were entirely determined by High Resolution Electron Microscopy (Σ = 5(310), Σ = 13 (320), Σ = 13 (510), Σ = 65 (1130), Σ = 25 (710) and Σ = 41 (910), the Σ = 13 (510) interface is the most interesting. It exhibits two kinds of structures. One of them, the M-structure, has tetracoordinated covalent bonds and is periodic (fig. 1). The other, the U-structure, is also tetracoordinated but is not strictly periodic (fig. 2). It is composed of a periodically repeated constant part that separates variable cores where some atoms can have several stable positions. The M-structure has a mirror glide symmetry. At Scherzer defocus, its HREM images have characteristic groups of three big white dots that are distributed on alternatively facing right and left arcs (fig. 1). The (001) projection of the U-structure has an apparent mirror symmetry, the portions of good coincidence zones (“perfect crystal structure”) regularly separate the variable cores regions (fig. 2).

Characterization of structural units in tilt grain boundaries

1992 ◽  
Vol 50 (1) ◽  
pp. 120-121
Author(s):  
Stuart McKernan ◽  
C. Barry Carter
Keyword(s):  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Structural Units ◽  
Symmetric Tilt ◽  
Resolution Electron ◽  
Special Cases ◽  
High Resolution Electron Microscope

General tilt grain boundaries can be viewed in terms of small structural units of varying complexity. High-resolution electron microscope (HREM) images of these boundaries in many materials show this repetitive similarity of the atomic structure at the boundary plane. The structure of particular grain boundaries has been examined for several special cases and commonly observed configurations include symmetric tilt grain boundaries and asymmetric tilt grain boundaries with one grain having a prominent, low-index facet. Several different configurations of the boundary structure may possibly occur, even in the same grain boundary. There are thus many possible ways to assemble the basic structural units to form a grain boundary. These structural units and their distribution have traditionally been examined by high-resolution electron microscopy. The images of the projection of the atomic columns (or the tunnels between atomic columns) providing a template for constructing “ball-and-stick ” models of the interface.

TEM Studies of Grain Boundary Structure in a Cast Polycrystalline Silicon

2005 ◽  
Vol 475-479 ◽  
pp. 1673-1676 ◽  
Author(s):  
Isamu Kuchiwaki ◽  
Takahiro Hirabayashi ◽  
Hiroshi Fukushima
Keyword(s):  
Electron Microscopy ◽  
Grain Boundary ◽  
Twin Boundary ◽  
Polycrystalline Silicon ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Grain Boundary Structure ◽  
Transmission Electron ◽  
Resolution Electron ◽  
The Difference

Cast polycrystalline silicon for solar cell contains mostly straight twin boundaries which are thought to have little effect on the electrical activity. There are, however, some complicated grain boundaries in it. One of these boundaries consists of slightly curved and straight parts. The structure of this boundary was analyzed to investigate the difference of these two types of boundaries. The conventional transmission electron microscopy (TEM) found that this slightly curved boundary was the zigzag shaped boundary made by (11 _ ,2) and ( _ ,211) planes. High resolution electron microscopy (HREM) confirmed that (11 _ ,2) plane was the boundary of {112} Σ3 twin boundary which formed a straight grain boundary at the other end of the analyzed grain boundary, and also confirmed that ( _ ,2 11) plane was also the boundary of {112} Σ3 twin boundary which intersected with the former twin boundary at an angle of 120 [deg].

Dislocation Structure of 10° Low-Angle Tilt Grain Boundary in α-Al2O3

2007 ◽  
Vol 558-559 ◽  
pp. 979-982 ◽  
Author(s):  
E. Tochigi ◽  
A. Nakamura ◽  
Naoya Shibata ◽  
Takahisa Yamamoto ◽  
K.P.D. Lagerlöf ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Dislocation Structure ◽  
High Resolution Electron Microscopy ◽  
Stacking Fault ◽  
Partial Dislocations ◽  
Resolution Electron ◽  
Tilt Grain Boundary ◽  
Α Al2o3 ◽  
Repulsive Forces ◽  
Edge Dislocations

Dislocation structure of 10º low-angle tilt grain boundary in α-Al2O3 has been observed by high-resolution electron microscopy (HRTEM). It was found that perfect <1120> edge dislocations, which are introduced to compensate the misorientation, dissociated into two mixed partial dislocations with {1120} stacking-fault in between. The distances between the two partials were estimated by the force balances between repulsive forces of periodical dislocations and attractive forces from stacking-fault. The stacking-fault energy for 10o low-angle tilt grain boundary was estimated to be much higher than the previously reported value.

Structure of Σ7 grain boundary in Al2O3

1994 ◽  
Vol 52 ◽  
pp. 718-719
Author(s):  
C. C. Chu ◽  
F.-R. Chen ◽  
C.-Y. Wang ◽  
L. Chang
Keyword(s):  
Grain Boundary ◽  
Atomic Structure ◽  
Coincidence Site Lattice ◽  
High Vacuum ◽  
Three Dimensional ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Cubic Symmetry ◽  
Grain Boundary Structure ◽  
Resolution Electron

In the past, extensive high resolution electron microscopy has been applied to the atomic structure of grain boundaries of cubic symmetry. In order to have a better understanding of generalization of the grain boundary theory, it could be fruiful to study grain boundary structure of non-cubic and low symmetry crystals in which case the exact CSL’s may not exist. Al2O3 has a hexagonal crystal structure ( non-cubic). In the case of hexagonal crystals, three dimensional coincidence site lattices (CSL’s) are only possible for rational values of (c/a), except for rotations about the [0001] axis. The (c/a) of α-Al2O3 is very close to a rational number (15/2) such that constrained coincidence-site lattice (CCSL) misorientations can be found. In this research, we study the atomic structure of Σ7 grain boundary. The misonentation of Σ7 is [011]/180°. The bicrystals of Σ7 were made by diffusion bonding in high temperature and high vacuum.Figs. 1 (a) and (b). show typical HRTEM images of Σ7 Al2O3 boundary recorded at the underfocus values -48 nm and -96 nm, respectively. The beam direction is parallel to a common axis [20].

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